1. Field of the Invention
The present invention relates to a system and a method for processing (e.g., cleaning) substrates such as semiconductor wafers and LCD glass substrates.
2. Description of the Related Art
Semiconductor device manufacturing processes include a cleaning process by which semiconductor wafers are cleaned by supplying a chemical solution to the wafers. A batch-type processing system which processes a plurality of wafers collectively is generally used for performing the aforementioned cleaning process. A carrier containing a plurality of wafers, arranged parallel with each other and spaced at regular intervals, is delivered to the processing system. A wafer conveyer arranged in the processing system removes the wafers collectively from the carrier, and delivers them to the processing unit, where the wafers are subjected to a predetermined process by using a chemical solution. The wafer conveyer removes the processed wafers from the processing unit, and returns them into the carrier. Such a substrate processing system is disclosed in US2002/0000240A1, for example.
For the purpose of inspecting the processing condition, some of the product wafers removed from a carrier are replaced with monitor wafers (i.e., dummy wafers), and the product wafers and the monitor wafers are processed collectively. Upon inspecting the processed monitor wafers, interactions between the wafers during the process (e.g., re-adhesion of a polymer removed from one wafer to another wafer) can be found.
In the past, the replacement of the product wafers with the monitor wafers was carried out manually by the operator. In this case, careful handling of the wafers was necessary, and it was possible that particles adhered to the wafers.
JP11-354604A discloses a substrate processing system provided with a wafer conveyer. The wafer conveyer has a robot arm, to which a plural-wafer carrying hand or a single-wafer carrying hand is selectively attached. The processing system is provided with means for automatically changing the plural- and single-wafer carrying hands attached to the robot arm. In usual operation of the processing system, the plural-wafer carrying hand is attached to the robot arm. The plural-wafer carrying hand transfers product wafers collectively from a carrier to a posture changer, which changes the posture of the wafers before they are loaded into a processing unit and after they are unloaded from the processing unit. If it is necessary to rearrange the wafers held in the carrier or the posture changer, the single-wafer carrying hand attached to the robot arm handles the wafers one by one. JP11-354604A teaches that the single-wafer carrying hand is attached to the robot arm, and loads monitor wafers and product wafers to the posture changer. This prevents the adhesion of particles to the wafers which could occur due to manual handling by the operator. However, the wafer-carrying-hand changing operation requires a certain amount of time. Moreover, if the product and monitor wafers are loaded to the posture changer one by one, a considerably long time is necessary. These result in deterioration in throughput of the processing system.
JP11-354604A also discloses another substrate processing system provided with a plural-wafer conveyer and a single-wafer conveyer, both of which are capable of accessing a carrier and a posture changer in order to transfer wafers therebetween. The plural-wafer conveyer is arranged at the lower region of a wafer transfer area and the single-wafer conveyer is arranged at the upper region of the wafer transfer area. When one of the plural- and single-wafer conveyers accesses the posture changer, the other conveyer rises or descends to a suitable vertical position where the two conveyers do not interfere with each other. However, in order to achieve the aforementioned arrangement and operation of the two wafer conveyers, the transfer area must be large-sized, and each of the conveyers must have a large range of movement. In addition, if it is required that monitor wafers are loaded to a posture changer together with product wafers, the product wafers must be first loaded to the attitude changer by the plural-wafer conveyer, and then some of the product wafers must be replaced with the monitor wafers by the single-wafer conveyer one by one. This operation requires a considerably long time, resulting in deterioration in throughput of the processing system.